The invention relates to laminated foils and more especially to plastic-based laminated foils which are free from elastic memory and which can be bent at room temperature into a permanent shape. These foils are comprised of a carrier layer of rigid polyvinylchloride (PVC), polyethylene or polypropylene, and a layer of aluminum bonded thereto.
The invention further relates to processes for jacketing straight, in particular insulated, lengths of pipe by forming shells, in the shape of a hollow cylinder, of the foil according to the invention around such lengths of pipe, and to the use of the foil according to the invention to produce wrapped pipes and for the manufacture of prismatic shaped articles.
Within the scope of the description of the invention, the term "foil" embraces foils in the shape of a foil web, in the shape of a length of a foil web wound up about the longitudinal axis to form a stock roll, and cut pieces, preferably rectangular cut pieces, of foil.
Within the scope of the description of the present invention, the term "polyethylene sheeting" is defined to embrace polyethylene sheets which exhibit a characteristic rigidity comparable with that of rigid PVC sheeting of approximately comparable thickness; sheeting made from polyethylene of high density (0.940 to 0.966) and high crystallinity (75 to 95%) is representative of such rigidity.
Polyethylene, polypropylene and in particular rigid PVC sheetings are all characterized by an inherent elastic memory at room temperature. One group of sheeting, which in the original state is virtually flat, tends, after being curved at room temperature, to independently and rapidly reassume, and to retain the original flat shape. In the case of another group of known sheeting of polyethylene, polypropylene and especially rigid PVC, such sheeting is, in the original state, in a durably highly curved condition and exhibits a powerful permanent elastic memory so that, after lying plane at room temperature, it tends to independently and rapidly reassume, and to retain its original curved shape.
The pronounced elastic memory of known sheeting made from rigid PVC, polyethylene or polypropylene, especially of sheeting having a thickness of from 200 to 750 .mu.m, is a disadvantage when the sheeting is used at room temperature, for example, for wrapping containers or pipes, inasmuch as it is only with special and additional measures that a single operative is capable of forming a cut piece of sheeting of appropriate length into a jacket around the container or around the length of pipe.
Aluminum foils have the disadvantage, in handling and use, that they are very prone to crease and have a low tear initiation and tear propagation resistance.